1. Field of the Invention
This invention relates generally to explosives and more particularly, to booster charges for detonating relatively insensitive blasting agents.
2. Description of the Prior Art
Relatively insensitive blasting agents, such as those of the ammonium nitrate/fuel oil (ANFO) type or the water gel slurry type, have found widespread commercial use. These blasting agents are characterized by an inability to be detonated by a commercial No. 8 blasting cap and require boostering to initiate detonation. Explosive boosters are compact explosive charges which are sensitive to blasting cap or detonating cord initiation and which provide sufficient energy to detonate a main charge of insensitive blasting agent.
Various booster compositions and designs are described in the prior art. See, for example, U.S. Pat. No. 3,037,452 and U.S. Pat. No. 3,037,453 to M. A. Cook et al.; U.S. Pat. No. 3,359,902 to J. J. Minnick; U.S. Pat. No. 3,371,606 to M.A. Cook; U.S. Pat. No. 3,604,354 to R. A. Brown et al.; U.S. Pat. No. 3,880,080 to M. A. Cook; U.S. Pat. No. 4,009,060 to H. F. Bluhm; U.S. Pat. No. 4,161,142 to D. W. Edwards et al.; U.S. Pat. No. 4,331,081 to J. A. R. Cloutier et al.; U.S. Pat. No. 4,385,948 to R. Reed et al.; U.S. Pat. No. 4,394, 197 to J. Kubik et al. Nearly all of the aforementioned inventions employ a cast charge of self-explosives or a dispersion of a self explosive in a formable matrix. The self-explosives used are generally trinitrotoluene, cyclotrimethylenetrinitramine, pentaerythritrol tetranitrate and the like. These self-explosives are inherently hazardous, especially when melted for casting and, in addition, are costly. The booster of U.S. Pat. No. 4,161,142 which contains no self-explosive, consists of a selected blend of ammonium nitrate particles and liquid fuel densely packed in a rigid package. This booster, however, lacks sensitivity and requires initiation by a small self-explosive cast primer charge. There remains a need for a booster charge which is safe to manufacture and transport, economic to produce, sufficiently powerful to initiate insensitive blasting agents yet sensitive to blasting cap or detonating cord initiation.